1. Field of the Invention
The present invention relates to an ethylene-α-olefin copolymer. More particularly, the present invention relates to an ethylene-α-olefin copolymer providing extrusion-molded articles excellent in moldability, optical properties and appearance.
2. Description of the Related Arts
As films and sheets used for packaging foods, pharmaceuticals, convenience goods and the like, molded articles obtained by extrusion molding of ethylene-α-olefin copolymers are much used. In these ethylene-α-olefin copolymers, excellent moldability is required. For example, there is disclosed an ethylene-1-butene copolymer which is obtained by copolymerizing ethylene and 1-butene with a catalyst formed from a catalyst component produced by reacting bis(indenyl)ethane, n-butyllithium and zirconium tetrachloride, silica, an organoaluminum-oxy compound and triisobutylaluminum, and which satisfies a specific relation between a melt tension and a melt flow rate of the copolymer and a specific relation between a temperature of the maximum peak in an endothermic curve of the copolymer measured by a differential scanning calorimeter and a density of the copolymer(e.g. U.S. Pat. No. 5,374,700).
In addition, there is disclosed an ethylene-α-olefin copolymer which is obtained by copolymerizing ethylene and 1-hexene with a catalyst formed from a co-catalyst carrier obtained by contacting diethyl zinc, pentafluorophenol, water and silica, racemi-ethylenebis(1-indenyl)zirconium phenoxide and triisobutylaluminum, and which has a melt flow rate within a specific range and satisfies specific relations between a melt tension and a melt flow rate and between an intrinsic viscosity and a melt flow rate(e.g. US 2004/0030082 A1), and further, another ethylene-α-olefin copolymer which is obtained by copolymerizing ethylene and 1-hexene with a catalyst formed from a co-catalyst carrier obtained by contacting diethyl zinc, pentafluorophenol, water, silica and trimethyldisilazane, racemi-ethylenebis(1-indenyl)zirconium phenoxide and triisobutylaluminum, and which has a melt flow rate within a specific range and satisfies specific relations between a melt tension and a melt flow rate, between a intrinsic viscosity and melt flow rate, and additionally between a chain length of a high polymer component and a melt flowrate(e.g. DE10339987 A1).
However, molded articles obtained by extrusion-molding the above-described ethylene-α-olefin copolymers, were not sufficiently satisfied in optical properties such as transparency and surface gloss, and further, the appearance thereof was sometimes deteriorated by formation of fish eyes.